US1127853A - Process of and apparatus for crushing ore. - Google Patents

Description

G. BEER.

PROCESS OP AND PARA'US FOR CRUSHING ORE.

APPLICATION ILED APR.10, 1914.

"Patented Feb, 9, 1915.

fifi

g @mmf H. G. BEER. PROGESS 0F AND APPARATUS FR ORUSBNG ORE. 4 APPLUATION IXLD APBAO, i914. y 19 3 Qfg, Emme@ M19, MM5.

2 SHEETS-SHEET 2.

pleted an average stroke must be considerable. The return -of the stamp on its up-y ward stroke, however is attended with a waste of power, when as. at present, the operating fluid is ordinarily admitted to and then exhausted at a lower pressure from such a large clearance space. To avoid these serious objections, my present invention among other things provides a means for permitting the up and down strokes to take place without admissions or exhausts of counter pressure air through valved open ings, and further provides a large volume of compressed air in continuous communication with the space beneath the piston. The down stroke is thus accomplished by a higher pressure acting on the upper face of the piston than beneath it, while the up stroke takes place by permitting an exhaust Jfrom above the piston at a pressure lower than that acting beneath it. For the sake of brevity in the ollowing disclosure the pressure acting beneath the piston will be called the counter pressure, and the air supplied to and exhausted from the space-*above the piston will be called the operating air. A high averageA pressure per square inch above the piston in excess of the counter pressure below it is obviously necessary with a piston of small size, inorder that the stamp head may reach the desired high striking velocity. But to use with economy the ordinary systems of steam or compressed air tansmis sion with an exhaust at atmospheric pressure or below, would require initial pressures much in excess of those found practicable. It' a high exhaust pressure could in :tact be used, then-the required ratio of expansion would also be lower and the initial. pressure would be less in excess of the average pressure needed 'to give the stamp the desired speed. But to secure economy of power in such cases the exhausted steam or air should 'then be entirelyV utiliI/.ed in driving other machinery operating coincidentlv with the stamp, a. method rarely practicable. ln the case of compressed air, on the other hand, the exhausted air might be utilif/ed in 'a motor arranged to assist in driving the compressor which provides kthe compressed air for operating the stamp. But it will be much simpler and more economical to divert the exhausted air to the suction of the compressor as in the present invention, thereby securing a llow rateo't' compresion with reduction ol compression temperatures and of the losses pertaining to such temperatures. This last :ase in fact represents a closed system of compressed air power transmis sion with high pressure both on supply and return, operating through 'suitable valves between the stamp cylinder and compressor. The application ot such a system, in connection with a continuously acting high pressure, operating without valves, and formingv a separated closedsystem for the space bc neatli the piston, constitutes the first and main idea of my invention. Since, as pointed out, the length of the piston stroke will in operation vary with the thickness of rock between the shoe and die, and with the permissible amount of wear between adjustments, the ratio of expansion of the air driving the piston downward must be such that for the longest stroke allowed the linal pressure after expansion will not fall too much below the counter pressure acting beneath the piston. ln other words a great excess ot' counter pressure before completion of the down stroke would cause the stamp head to lose too much velocity and therefore in force of impact, which latter it is one of the main objects of this invention to maintain. The work done on the up stroke by the excess of counter pressure over exhaust pressure is imparted to the mass of the stamp as energy of motion, and this energy, through closing oft' the exhaust at the proper point of the stroke, is transferred Jfrom the stamp to the air above the piston, first by compression of said air to about admission pressure, and thereafter by forcing part of the air so compressed into the admission valve chamber and the spaces connected therewith. rthe work thus transferred to the air is obviously again available to assist driving the stamp on its next down stroke. rlhe une avoidable variation in the length ot' the stamp stroke will obviously cause the emrrgy oil motion acquired by the stamp on its up stroke to be greater for a long stroke than for a -short stroke, and hence more work ywill be taken up by the air above the piston after closure of the exhaust in the former case than in the latter. Since the work of compression will always be the same, the difference will be in the displacement of the amount of air into the admission chamber, so that for the long stroke the piston will approarh closer to the upper cylinder head than in the case of the short stroke. lt thus will be clear that with the manner of operation described a considerable clearance space above the piston will not aliect the economy. Ample clearance may therefore be provided to safeguard against the pistons striking the cylinder head in case oi air leaks past the piston, or derangement of the mechanism causing an up stroke oi unusual energy.

Referring to the drawings: A represents the stamping machine proper, .ll a reservoir oi high pressure air, connuunicatiug with the upper end of the stamp cylinder 1 by means oit" the pipe 2. The lower pressure air' l) is a reservoir of counter pressure air, in

free communication with the lower end of memes the stamp cylinder 1;- While at E is shown ,a compressor adapted to draw air from the exhaust reservoir C to compress it to the admission pressure, and to force it into the high pressure reservoir B, as will he more fully explained hereinafter. The small compressor shown at F is used for making up the air lost from the system b1 leakage and for this purpose it is adapte to draw air from the atmosphere and compress it to the exhaust pressure existing in C, as will likewise appear hereinafter.

Referring to the stamping machine proper, the mortar box fl has fitted in its base the die 5. The feed opening for the rock is at 5 on one side of said box and the discharge opening 7 with the soreen is loeatedon the opposite side. r1`he chute 9 conveys the rock to be crushed to the feed opening 5. The stamp head 10 of the stamping machine has at its lower end the shoe 11 said shoe heingsecured with its dovetail lug A 12 by means of the key 13 to arecess in said head as shown.. T he upper end of the head 10 is provided with a screw thread 11i, over which is screwed the cap 15. The piston roll 16 passes through an opening 17 in the top of cap 15, and is formed at its lower end with the disk 18, which latter is thus inelosed in 'the space between the top of the stainp head 10 and the cap 15. bove and below disk 18, are provided elastic cushions 19 and 2() which may be of rubber or compressed air, forming;` an elastic connection between the stamp head 10 and the piston rod 16. At the upper end of rod 16 is se cured the piston 21. The upper end ot' the stamp head 10 with its cap 1.3 is guided vertically in the bored guide Q2, which is supported on the pedestal trame 23, and has at its upper, end the extensions 2l, 2l, hy which it is joined to the lower head of the stamp cylinder 1. e

In order to provide for the vertical adjustment of the stamp cylinder 1, so as to allow for the gradually lowering position of pistonQl, due to the wear of the die 5 and shoe 1l, there is placed between the flange 2G on guide 22 and the corresponding liange 27 on the pedestal 23, a plate ot a certain tliiclr` ness when the die 5 and shoe 11 are new. This plate is then replaced by a thinner' one when the die and shoe become worn a cer tain amount, and as the wear proceeds still thinner plates 28 are inserted, so that the lower surface of shoe 11 will always be permitted, notwithstanding the wearing away of the parts, to work substantially at a 1naXimum of ellicienoy. justmcnt may obviously he used, the one here described serves to illustrate one example of such adjustment.

The pipes' 2 and 3 connecting the stamp cylinder 1 with the reservoirs B and C are preferably provided with flexible sections Other methods of ad-A yinder 1 by the short pipes 31 forming part of their-ee communication between reservoir D and the spaee heneatli piston 21. .For the purpose el making up air losses and for filling with air at the start the small pipe connection 77, Z7 communicates between reservoir D and the high presser. pipe t2 at a point 32 between cylinder 1 and the ilexi* lele connect-ion 29. At 7S 1 provide a. reduoing valve in the pipe 77 #for limitiiig the pressure in reservoir i 1n the lower part or the stamp cylinder' barrel 1 there are a number of openings 33, 33, atording a .tree communication with the annular chamber 34%, connected through pipe 31 with the counter pressure reservoir D and causing the Apressure existing in reservoir D to act continuously on the under side ot piston :'51 longl as the latter remains above the circle of openings 33, These openings are located at such a height in relation to 'the piston travel, that if during the operation of the stamp head. 10 the feed o1 roch to the mortar l should tail, so that there would he no layer of rock on the die 5 to taire up the energy stored in the descenoing stamp, or if the shoe 11 should break, then the piston 21, inpassing the said openings 33, will automatically close ott communication ofthe space 35 1eeneatli it. with reservoirl), and cause the moving masso stamp andv piston to spend a large part of its energy of motion in compressing the air, thus trapped or imprisoned beneath the said piston 21. The effect of thus automatically trapping the air will loe to materially reduce the force of the hlon7 which would otherwise fall on parts of the machine., Which are not as yielding as the hed of rock. Ilhe reason' for having a number of openings 33, 33 is to provide area as large as possible and of a minimum height for the unobstructed flow hack and forth of the counter pressing air, while at the same time to reta-in a metal sur- .face at frequent intervals around the circumference of the cylinder to properly guide the piston 21 :is it passes over the openings 33,

1n Fig. 1 the stamp 10 with its piston 21 is shown at the lower end of the stroke and the rock on the die having just been crushed. has absorhedthe full energy of the stamp blow. The upward or return stroke'begins as soon as" the pressure above piston 21 is Sutheiently reduced by the opening of exhaust valve 3G, located in the lateral chamber 3T nca'r the upper end cylinder 1. and 'controlling communication with exhaust res-y ervoir (l through chamber 50 and pipe 3. In Fig. 1 valve 36 is shown in'its closed positionV bein held to 'ts seet by the s rino' 38, f

a g .l Y P e The chamber37 opens into cylinder 1 at port 39, which is given a very much less area than the aggregate of the ports or openings 33, 33, because the nal piston speed on the up stroke z'. e. during the exhaust, is much less than the velocity acquired during the down stroke, and therefore a less area for port 39 suflices. The beginning of the eX- haust bythe opening of valve 36 is controlled independently of the movement ot' the stamp head 10 and takes place at such periods that the stamp head 10 may, without material retardation, complete its longest permissible stroke. The opening of the said valve 3G as will now be explained is preferably accomplished by a small electric, or air motor,

as shown at 40 mounted on the bracket 4l at the side of guide Motor l0 drives by pulley 42 through belt 43 the pulley fiel mounted on cam shaft 45, which latter is carried in bearing bracket 4G and has mounted on it the cam 47. Cain 17 works against a vertical lever 48, fixed on the outer end of a shaft 49, which passes airtight through "the side Wall of chamber 50, located below valve 36 and connected by pipe 3 to reservoir C as shown. Inside of chamber 50 there is mounted on the shaft e9 a. horizontal lever 51, which bears against the lower end ot' the 3o stem 52 of valve 36. .As cam 47 revolves it osci'llates lever 48, thereby elevating inside said chamber 50 the lever 5l and thus lifting valve 36 against the pressure of spring 38. The closing ofvalve 36 takes place when lever 48 is released by cam i?, and said closing is' so timed, that it takes place .as soon as possible after the piston 2l on its upward stroke has passed and thereby closed the exhaust port 3l). The eiiect of the ar- 40 rangement described is: rllhe Vexhaust is opened at the proper moment,independently of the movement of the piston 2l, the closure of the exhaust takes place during the regular operation dependent only on the distance of the piston from the upper cylinder head as it approachesthe latter and independently of the separate later closure of the haust valve 3U. These -features are important to the proper operation of the stamp. 5c, The piston might of course be so arranged as to act on the exhaust Avalve and close it by means of a mechanical connection, instead ot' by the simpler and more positive expedient of having the piston act as a valve '55 itself.y But such less reliable means would only carry out the same idea of closing the independently opened exhaust oy the upward movement ol the piston. .The port 23S-l is located at such a distance below vthe upper cylinder head, that during the normal operation o the piston` the work stored in the upward movement mass of stamp and piston will, a ller the latterl lias'closed the said port 33t), be spent in doing useful work on the air a5 imprisoned above it. This work will consist at vfirst in compressing the air to about the admission pressure, thereby opening the admission valve 54, located in valve chamber 55 in the upper cylinder head 53, and tl after in displacing air of admission prt c past valve 5ft into chamber 55 and lesen voip B, connected to said chamber by pipe 2.4 After the energy of the upwardly nim ing stamp has been thus spent there must still remain as a safety precaution some dis-- tance between the top of the piston and the. underside of the cylinder head. When the, piston is at or near the, upper end of its stroke it is obvious that communication with reservoir C and the pipe system under its pressure must be closed, for otherwise the counter pressure air in cylinder l would rush from the space beneath the piston into said pipe system. This is prevented by making the piston 2l sulliciently deep, so that its lower edge, when in its highest position, does not uncover port 39; or l may also prevent the same, by so timing the parts that exhaust valve 36 will have been closed by its. operating connections before piston reaches a position where its lower edge uu covers port 3S). Exhaust valve 3G must, hoe ever be closed in any event before the upper edge of piston 2l on its denvnward stroke uncovers port 39, so that air under admission pressure may not rush into the said pipe system or the exhaust space 50.

The admission valve 5i is formed with its i.

upper part 56 as a ton capable' of slid` ing` airtight in a vertical direction in the bore o?, the upper part ot' which bore forms a chamber above said part 56. rhe spring .3S holds valve 5l to its seat 59. A duet GU leads from bore 5T laterally and then down through the wall ot cylinder l, where it issues into the interior of said cylinder at the small ports 6l and 62. 'lf he lower of these ports (l2, is located at such a height, that the lower edge ot piston 2l will have passed and uncovered it on its upward stroke, bei'ore the upper edge of the piston has closed otl' exhaust port 39 as is indicated .in dotted lines Fig. l. Counter pressure air 'from reservoir l.) in vthis position accordingly acts through duet (30 on the upper 'l'aee oli valve piston 5G .to maintain the same closed before the exhaust port 3U is closed. The pressure thus acting is reinforced by that due to springr 5S, the strength of which is so proportioned as to cause the compression of the air imprisoned, as piston 2l rises, to reach about the admission presf sure. before the admision valve 5l Ywill be llilted otlI its seat by the pressure oi' .such

imprisoned air acting on that part of the area oiifvalve 5l exposed by the valve opening 63. As soon as valve 5l however has been thus opened by compression ol the air beneath it, its entire lower surface will be expcsedgto the ladmission pressure from admission pressure by the energy of`motion' of the 'preceding up stroke of ythe stamp fie head and piston and the the piston, the down stroke proceeds under full admission pressure until the admission valve closes at that period of the .down

stroke corresponding to the point 102, the

ldistance traveled or volume swept by the piston being represented bythe distance frompoint 115 to point 102. F rom now` on the down stroke proceeds under the expansion of the airto the end of the piston comparing the small areas rel'n'esentingy f slightly retarded rby the points 103,117, and 119.

` the .separate takes place .from above the piston at the stroke represented at point 113. vThe final pressure represented by the distance between line 1000 and point 113 .exceeds the counter pressure represented by the distance between lin'e 1000 and point 112 by an amount measured by the distance'betwcen points 112 and 113, and exceeds the exhaust pressure represented by line 1050 by an amount measured by the distance between points 113, and 1111'. The triangular .area indicatedby points 113, 101 and 1141 represents the theoretically irrecoverable loss of energy byl limiting the stroke to the point 112.y In the case of the longest stroke ex plained in the diagramKFig. y3 the stroke, which is measured by the distance between points 116 and 117, or by line 1160 starts? at point 120, the/piston being nearerto the cylinder head than inthe case ofthe slibrtj stroke, as indicated by the length of liiie 1200, being lessthan the length of line 1150 in Fig. 2., Expansion begins' at the same point 102 from thecylinder head as in the case'of the short stroke, but as the stroke is much longer, terminating at v117, the 'pres-` sure now drops below ,the counter pressure indicated by line 1090' by an amount measure/d by the distance between the points 11 a gradually increasing excess of counter pressure. The energy thus .taken from `the stamp is, however slight, being measured by the area indicated by A further slight irrecoverable loss is measured by the area indicated by the ooin'tsl119, 104 and y118. The losses indicated, asidefrom friction and 'losses due to temperature fa.ll, \are those theoretically irrecoveiable. `Vh`en them with that representing the total work, it appears that they can bekept very small by si'iitablc choice ot operating pressures.

'lheexhaust having been opened about the time o1 completion of Vthe down stroke, by .motor referred. f to, 'exhaust admission port be-v ing open, also through the same action of and 119 so that the stamp is being short strokes.

pressure indicated by line 1050.being less y Athan the counter pressure indica ted by line 1090 extending between points 103 and 100 by the amount indicated by the distance between points 103 and 121, by which excess of pressure the pistonis inipelled upward until it closes ofi' the exhaust at point 105.

At the peint 106 the pressures above and' below the piston have become equalized and the mass of stamp and piston have acquired their full energy of motion. F rom now on the energy so gained is again spent in doing work on the air imprisoned above the piston. The' first part of this work will consist in compressing the imprisoned air from the pressure atpoint 100, now equal to they counter pressure indicated byf the distance soy between points 103 and 109 oi' by line 1000 I to about admission pressure indicated by line 1010, thereby forcing open the admission valve 51, Fig. 1 as previously explained. The remaining energy o't the upwardly moving stamp is spent in torcing air at adl mission rpressure past the admission valve into the valve chamber 55 and the reservoir B. The total compression and displacement work thus performed on the air is repreenergy of motion than for thefshort stroke,

so that after the work of compression is 10S counter pressure acts, obviously gain more completed at 107, there is also a 'greater amount of energy remaining in the mass of the stamp, which energy must be absorbed in forcing la larger volume ofv air aga-inst Aadmission pressure, and since this pressure is constant, the distance required to'take up the greater work must be longer, as indicated by thedistance 107, 120 being greater than the distance 107,I for the short stroke. The diagram ,of themcompressor E will be the saine for both the `long and the If there wereI no resista-nce or temperature losses its aniount would be represented rby the area. of the diagram 104,

.102, 107, and 105. In other words this area' represents that part of the compressor work,

" which is carried in the form oi' compressed air to the stamp cylinder after deducting all Y losses of compression and 'transmission of said air. By placing the compressor as close.

to the stamping machine as possible the heatI losses in transmission can be kept'small by. suitably covering the pipes. ltlective heat insulation is here favored by tue small. temj f perature rangeidue to the moderate comi pression ratio o1'v the closed yQvstem.

lit will be clear from the preceding scripti'on thet'fin recoinpressing the air re quired forthe operacion of rhs ssnp from` exhaust'pressure o admission pressures che compressor E lis sided by Lhe Norisy of the piston dunne' die letter eert of its upsiroire the enerxr'y' lor 'which Work he Jison and @i y l stump head obtained from the excess ofcounter pressure over exheusr pressuresctshown in Fig., l.; ss 4by closing; she vulve 36, admitting' counter pressure from reservoir l? iure cyliucler l under pistou Sli; and Ihen opening by hunrlvrelve 65 to sdmi into reylimler l :more seid, pis-'Lon :rmission proef sure from reservoir lli he paris are not suitably acljushzd9 the shoe il een he reise or lowererl by @aching up the cylincler i und inserting;r sirips 28 becween che flung/ges 26 and. 2'? o bring the lower surfuce oi shoe iler the ilesircfl dissuce ula-ove die 5. The. flexible connections 29 und Bil in and 3 pei-init seid pipes to unfler such erijussments. 'Seial efljustnienls ere also merle to compensate for 'weerom she shoe 1i smi (lie Si. lint as `@this *weer is noi compensaecl for untilit hss reached e preieiermined (legi-ee, Ache suiri shoe Ywil-i make shori snel long' 'sirolres shove explained and the energy chureoreristics of hese strokes ure indi sied in 'che fliegrams of Figs. 2 and lt is 'desirable to provirle e considerable space -in che cylinder l below he ports as illustrated, in order that the sir muy oe trapped in 'seid space und cushion any abnormul down strokes of piston 21. @n the upstrolreor .said piston zuisomusicslly closes the exhaust pori; and traps sir hetween, its upper surface sud' the cylincier "heuri, iherelay compressing it to zulrnission pressure. The energy stored in this iry is lutter returned, so the es shove er plainedg'and. While suirl'air is being thus eompressecl, the valve 5l' is hele 'to its sees not only by the spring 58y but by, che pressure of theuir from Icounter pressure reservoir Il, which passes through chanuei 60 to the 'top ci? vulve As the piston 21 coniuues to rise, however, the compression ol the air thus cropped will reach such e point that vulve 54k will open thus perxlfiiiw ring pressure from reservoir B io counter balance that on che rcp oi Valve The piston will ncrv descend. under full admis sion pressure from reservoir E until .it pisses und uncovers hc ports 6l 4to sinis sion pressure from reservoir lf3. vWhen sind port (il is thus uncovered, air si, mlmission 'pressure passes up chunnel 60, balances the pressure ou the lcweri'sce of miveii ami permits springe? to close seid valve, Where esce @y upon1 the` piston 2i proceeds on iis clown stroke under the expansive force oi' the air and under the action of gravity.

The exhaust vulve 36 .is operated independenly of thepiston 2l by means of the motor l0 uml its connecioos. The counter pressure reservoir D supplies air et a less pressure izlisn thus in reservoir B, to lift *the piston, :incl thisi-air is noi permitted to escupe pest the vulve 36 out of the cylinder l. lt forms scriJ ci cushion or counter pressure sufficiently powerful to resi/ore the paris Whiie not preventing the attainment of high downwnrii.y velocities on striking. riince this counter pressure air is not exhausted from the system the energy losses here-l toforc experienced in returning the parts `ure obvieted by roy invention. ln other words, it will' now he @leer that my presen?l sysem provides a large volume of com'- pressecl sir in reservoir D always in communication with lle lower surface of rhs piston, that the :iown srolre is. accomplished by s higher pressure from reservoir B on the upper surface ci seid pison, end that 'he pissen 2l is reurnefi by providing an eshsus, of the' air vshove the-piston ino res ervoir C as e lower pressure than `exists in reservoir B. lit Wili :further now be clear rims by my process or providing this intern mediate counter pressure in reservoir D, and livel-ting the exhaust air of reservoir C to the suction side ci a compressor which returns said air at admission pressure to reservoir i3, that a maximum of energy in the exhausted sir is ssrecl to the sysiem, so that l aroifl the heavy losses experienced irl-the olil systems. I further by this process secure u. low rute of compression and a re duction of compression temperatures and of tireless-es perruining to such icemp'eratures In fact it will now be clear thst my mechanien; constitutes e closed system with high pressure -both on supply and return, acting through :1 compressor, coupiecl with, an intermediate closed counter pressure system, shore being no energy loer ighrough exhausts to the smosphere.

lt is obvious that those skilled in the art muy vary the details of construction as well as the arrangement of parts Without depart ing from the spirit of my invention and herefore l ilo not wish te be limited to the alcove disclosure except us muy be required hy the claims.

lihut l claim is:

l, ln n stamping machine the combinetion of n reservoir for' containing air at ndmissiorfpressure; a reservoir for containing sir it 'exhaust pressure; n counter pressure reservoir for containing air nte pressure inern'lerlia-te said first two reservoirs; u cylinder; u piston in seid cylinder; a stamp hond connected to seid piston; connections beixwecn said irst named reservoir and the top of said cylinder; connections between the bottom of said cylinder and said third named reservoir; exhaust connections be-` tween the top of said piston and said second named ieservoir; a compressor; connections between the suction end of said compressor and said second reservoir; and connections f between the-delivery end of said compressor and said iirst named reservoir, substantially 'as described.

2. In a `stamping` machine the .combinai'icn of a reservoir for containing air at admission pressure; a reservoir for containing v air at exhaust pressure; afcounter pressure reservoir for containing `air at a pressure intermediate said first two reservoirs; a cyl- K n inder; aV piston in said cylinder; a stamp head connectedv to said piston; valvedcon-k neet-ions between said first named reservoir and ytheftop of said cylinder; valvgessconriections between the bottom of said: cylinder and said third named reservoir; valved exhaust .Connections between the top of said piston and said second named reservoir; a

compressor; connections between the suc! tion end of said compressor and saidsecond reservoir; and connections between the delivery end of said compressor and said first" named reservoir, substantially as described.

3. In a stamping rmachine 'the combination of a reservoir for containing air at admission pressure; a reservoir for containing air at exhaust pressure; a counter pressure reservoir for containing ai-r at a pressure intermediate said rst twov reservoirs; a

valved connection between said yiii-st named* Y. and said last named reservoirs; a1,ylinder; A

afpiston in saidfylindem a staii'ipliead conected to said*r piston; connections: between saidI first named reservoir` and vthe top of .A said cylinder; a valve controlling sai-d last named? connection; a. connectionv between said .third named reservoir and the top of said valve when said cylinder .is atr theend n .y of its upward stroke; connections between the bottom ofsaid lpiston and said thirdl named reservoir; exhaust connections between the top of' said cylinder and said sec-"- ond named reservoir adapted to be closed by said piston at a predetermined period of its stroke; a compressor; connections beL tween Athe suction end of said compressor and said secondi reservoir; and connections between the delivery end of said compressor :ind said i'irst named reservoir; substaning the air thussupplied at eihaustpres-` i sure lronisaid cylinder; a' compressor having its suctionr side connected to'said `second named reservoir and its delivery side connected to said first named reservoir; anda third reservoir for continuously supplying rair under said pistonat a pressure between those existing in said Hrst and second named reservoirs,'substantially as described.

5. In an o re stamp the combination eta stamp head; a piston tor operating said head; a cylinder in which said piston moves up and down provided with clearance spacesL above and below said piston in which the ously .supplying air under said piston at a pressure between those existing in said first and second named reservoirs, substantially as described.

6. In an ore stamp the combination of a stamp head; a ypiston for operating said head; a cylinder in which said piston movesy up and down provided with a space at its lower end'in which yairmay berk trappedon anv abnormally long'down stroke of said piston; a reservoir for supplying air under admission pressure to said cylinder on top of said piston; a reservoir for receiving the air thus supplied at exhaust pressure from said cylinder; a compressor having itssucytionfside connected to said second named* reservoir and its delivery side connected to said first named reservoir; `a second com- E' presser for supplying air :tromthe atmos pliere to said secon-d ynamed reservoir; anda third reservoir and connectionsconstituting a closed system for continuousl'v supplying air under said piston' :it a pre re between those existing in said first and msecond named reservoirs, substantially as described.

7. The process of operatingiore stamps which-'consists in supplying compressed air to a movablefinemb'er at admission pressure and against a continuous counter pressure of an inclosed volume of air; exhausting said first named air to a compressor ata pressuredess thansaidwcounter pressure; and compressing said exhausted air to admission pressurev again, .and resupplying the same to said movable member, substantially as described. y f n 8. The processof operating ore stamps which consists in providing acontined volume of air under pressure for continuously acting on the under side of the stamp piston; causing a confined volume of air at a yhigher pressure to intermittently act on the t,top side of said piston; exhausting the y air f thusadmitted to the top of said pistonat a pressure lower than said first named air to 1n testimony whereof aix my signa.-y

the suction side of a compressor; and recomture, n presence of two Wtnsses.

pressing said exhausted air to its initial HANS CHARLES BHR. presse and returning the same to the top Witnesses; 5 side of said piston, substantialy as de- JOHN KENNALLEY,

scribed. E.- S. DANNATT.

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